906 GEOLOGY OF OHIO. 



Gallia Gallia county. 



Star Jackson county. 



Vinton Vinton county. 



Union Hooking county. 



It is also known to be worked at all of the eastern furnaces of Jackson 

 county. There is no characteristic by which the most experienced iron 

 master of the district can distinguish a specimen from the Hecla Fur- 

 nace from one taken from Nelsonville or Gore. 



The gray ore consists of oolitic grains of carbonate of iron, which are 

 each invested with a whitish covering of fire-clay and finely divided 

 silica. It contains in this state about thirty to thirty-five per cent, of 

 iron. The outcrop ore rises frequently to forty-five and fifty per cent., 

 and yields in the furnace over forty per cent. 



There is scarcely a trace of sulphur in the ore, and phosphorus, exists 

 in very small proportions. 



Its average thickness in Southern Ohio may be taken as ten inches, 

 but north of Vinton county, the average does not exceed eight inches. 

 Locally, however, it rises to several feet in thickness. From less than 

 one-half acre near McArthur, on the " Speed farm " of Dr. Wolfe nine 

 thousand tons of ore were taken. 



The steadiness an constancy of the seam go far toward making amends 

 for the scanty volume. It is found where it is due and can be followed 

 under cover with confidence and success. Several of the older furnaces 

 of Lawrence county obtain a large proportion of their ore by drifting. It 

 is subject to cut-outs of course, but there are as few in this seam as in 

 any other geological horizon of the district — a district by the way that 

 is remarkable for the steadiness of its series. 



More than sixty Ohio furnaces make this ore their chief supply, and 

 the iron yielded by it is the standard of quality throughout the Ohio 

 Valley. 



11. At an interval varying from thirty feet in the northern counties 

 to fifty feet in the southern counties, another very steady seam of ore 

 occurs. In the Kentucky furnace district it is known as the " Black 

 Kidney " and is there highly esteemed. It has no generally received 

 name to the northward, but it will be recognized by all familiar with the 

 geology of this district from its relation to Coal No. VI, with which it is 

 closely associated, underlying it at an interval of two to ten feet. It is 

 a very compact and close-grained, blue carbonate, lying in large blocks 

 and kidneys, m the clays that support the coal. It is also characterized 

 from the Hocking Valley to the Ohio River by holding beautifully pre- 

 served coal plants. Leaflets of ferns, bits of bark, and branches are 



